1. FIELD OF THE INVENTION
The present invention relates to surface-coated cemented carbide articles and a process for the production thereof and more particularly, it is concerned with cemented carbide articles or parts, for example, cutting tools having one or more coating layers of oxides, carbides and nitrides.
2. DESCRIPTION OF THE PRIOR ART
Cemented carbides are sintered products having suitable toughness and wear resistance containing one or more carbides and/or carbonitrides of one or more metals selected from titanium, zirconium, hafnium, vanadium, columbium, tantalum, chromium, molybdenum and tungsten, cemented by mainly one or more metals from the iron groups. In the case of using these cemented carbides as a cutting tool, it is an important problem to increase the wear resistance since the tool life depends on the wearing of its edge. A number of proposals have thus been made to coat the cemented carbides with one or more layers of carbides, nitrides or carbonitrides of titanium, zirconium and hafnium and oxides of aluminum and zirconium which have more excellent wear resistances than the cemented carbides, thus obtaining coated inserts excellent in not only toughness but also wear resistance. However, these proposals are not only directed to the increase of the number of coating layers or to the change of the variety of coating layers and do not serve to improve or keep well the toughness of the cemented carbides.